DNA and RNA Flashcards
1
Q
Nucleotide
A
- phosphorylated nucleoside
- base joined to sugar-phosphate unit
2
Q
Nucleoside
A
-consists of nitrogenous base and pentose sugar
3
Q
Nitrogenous bases
A
- Adenine-purine
- Guanine-purine
- Thymine-pyramidine
- Cystosine-pyramidine
4
Q
DNA
A
-pairs of nucleotides joined with hydrogen bonds
TA or AT
GC or CG
5
Q
Gene
A
- subportion of DNA
- codes for polypeptide sequence
- length depends on size of polypeptide coded
- 3 adjacent nucleotides is called a codon
- each codon codes for specific amino acid
6
Q
Exons
A
- polypeptide coding sequence in DNA
- interrupted by non-coding introns
- introns are removed when mRNA leaves the nucleus
7
Q
Transcription
A
- synthesis of RNA from nuclear DNA
- takes place in the nucleus
- transcripted RNA contains introns that do not code of polypeptides
- splicing then occurs, aided by nucleosomes in the nucleus to remove non-coding sequence and results in messenger RNAs
- Transfer RNAs are also synthesised from DNA in the nucleus by a separate process
8
Q
Translation
A
- refers to the production of proteins from RNA
- takes place in the cytoplasm
- aided by the ribosomes
- ribosomes can be seen attached to rough endoplasmic reticulum
- transfer RNAs are attached to specific amino acids according to their codon sequences
- these bind to various sites alone the mRNA in a zipper-like fashion
- initiation , elongation and termination occur
- termination is signaled by UAA, UGA and UAG
9
Q
Modifications
A
- take place in endoplasmic reticulum and golgi bodies
- also selects wrongly folded proteins to enter lysosomes for destruction
